Patent GB-757694-A (GB)
Title: Apparatus for making perspective drawings
Inventor: SCANDRETT ERIC VINCENT
IPC: B43L13/14
Filed: 1952-05-22
Abstract: 757,694. Drawing appliances. METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. May 21, 1953 [May 22, 1952], No. 13016/52. Class 11 Apparatus for producing a perspective drawing of an object 10 from a plan and elevational views thereof comprises a plan support 14 (Fig. 2) having aligning marks 11 whereby the plan view may be correctly positioned with respect to a viewpoint 12, markings a, b...i,  on the support for indicating the horizontal co-ordinates on an assumed picture plane 13 of points in the picture as viewed from the view point, a support 14a (Fig. 3) for an elevation of the object 10, and a radial cursor 16 pivoted about a point on the support 14a corresponding to the point 12 whereby the vertical co-ordinates in the same picture plan of points on the object may be determined for producing a drawing of the view in the assumed picture plane. The apparatus is designed for a viewpoint 12 at a predetermined fixed perpendicular distance from picture plan 13. To plot a point p on the object a line 15 is drawn from the view point 12 to the point p on the plan support 14 and the ordinate y of the point where the line 15 cuts the picture plane 13 is noted on the foreshortened picture plan 13 on the elevation support 14a. The cursor 16 is then positioned so that a line can be drawn to cut the line y y from the point 12 to the point p on the elevational view. The ordinate and abscissa of the point are then plotted on the sheet on which the final drawing is to be made. Other points are plotted in a similar fashion. The apparatus may be provided as an integral unit on a hinged beard 35, Fig. 5, bearing a plan chart 18 having guide lines 36, 27 and having a plan view of the object located so that the elevational view is viewed by looking in the direction of one of the lines 36, 37. A cursor 19 pivoted at a point corresponding to the viewpoint 12 is provided which is operatively connected to a transparent elevational arm 20 and a picture ordinate arm 22, both of which are slidable on a bar 21. As the cursor 19 is moved into coincidence with a given point on the plan view so the arm 20 is moved so that it corresponds to the co-ordinate of that point on the elevational view which is positioned before,it. The arm 22 is similarly moved to a line passing through the co-ordinate of that point on the sheet 25 on which the perspective drawing is to be produced. A cursor 23 is then moved so that it passes through the given point on the elevational. The point where the cursor 23 intersects.the arm 20 gives the ordinate of the required point and this point is then plotted on the sheet 25, the coordinate of the point being determined by the position of the arm 22. Other points are similarly plotted. The cursor 23 may be pivoted about a variety of points. The points 39, 39<SP>1</SP>, 39" are used when the plan view is positioned with respect to the line 36 and the points 38, 38<SP>1</SP>, 38<SP>11</SP> are used when the plan view is positioned with respect to the line 37, the line, 36, 37 determining which side of the object is to be drawn as being nearer to the viewer, and the points 38, 39, 38<SP>1</SP>, 39<SP>1</SP> and 38", 39" determining whether a view from above; an intermediate view, or a view from below are required. The apparatus is designed for use with a predetermined view point 12 and the point determines the plan and elevational views required. The drawing produced, however, will not necessarily correspond with a view from the point 12, but will depend on the positioning of the views on their respective supports, and in the case of the apparatus of Fig. 5, on whether the line 36, or 37 is used and on the point about which the cursor 23 is pivoted.